Now that we have this function, where we once used...<?php$idxLast = count($arr) - 1;?>we can now optimize code speed by using...<?php$idxLast = (array_key_last($arr) ?? 0);?>Use-cases include lots of looping and control-structures.If you do not know ahead of time that the array is numerically indexed, and that it could possibly be associative...safer/faster to stick with count().